Separation of Pd and Pt from highly acidic leach liquor of spent automobile catalysts with monothio-Cyanex272 and trioctylamine

The objective of this work is to directly separate Pd, Pt and Rh from highly acidic (6~8 mol/L HCl) leach liquor of spent automobile catalysts with commercial extractants monothio-Cyanex 272 and trioctylamine (TOA). The effect of various parameters such as the acidity, extractant concentration, phase ratio A/O and diluents on the Pd and Pt extraction were investigated. The stripping behaviors of Pd and Pt were also studied. We also separated Pd and Pt from highly acidic simulated leach liquor of spent automobile catalysts with monothio-Cyanex 272 and TOA. The results show that monothio-Cyanex 272 shows strong extractability and specific selectivity for Pd, and only one single stage is needed to recover more than 99.9% of Pd, leaving behind all the Pt, Rh and base metals of Fe, Mg, Ce, Ni, Cu and Co in the raffinate. The loaded Pd is efficiently stripped by acidic thiourea solutions. TOA shows strong extractability for Pt and Fe at acidity of 6 mol/L HCl. More than 99.9% of the Pt and all of the Fe are extracted into the organic phase after two stages of countercurrent extraction. Diluted HCl easily scrubs the loaded base metals (Fe, Cu and Co). The loaded Pt is efficiently stripped by 1.0 mol/L thiourea and 0.05~0.1 mol/L NaOH solutions. Monothio-Cyanex 272 and TOA can realize the separation of Pd and Pt from highly acidic leach liquor of spent automobile catalysts.